Which of the following statements about email marketing is accurate?

a$.$

Email marketing is a helpful, unintrusive way to introduce target audiences to a marketer's brand for the first time.

b$.$

Email marketing offers a higher return on investment $($ROI$)$ than many other digital marketing tactics.

c$.$

Email marketing performs well with audiences on desktop screens, but not mobile users.

d$.$

Email marketing is more efficient if the marketer purchases verified email address lists instead of manually collecting addresses.